Polyploidy breeding

Polyploidy breeding procedure

1. POLYPLOIDY BREEDING

2. Chromosome no.- 3 types – haploid, diploid, basic number Haploid / gametic chr.no . (n) – half of somatic chromosome no. Diploid /zygotic chr . no.(2n)- Somatic chr.no . Basic no. (x) – gametic chr.no . of a true diploid species/minimum haploid chr.no of a species In regular diploids, 2n=2x

3. Polyploidy

4. POLYPLOIDY BREEDING

5. Suitability of a crop for pp breeding depends on following factors: Crops which are not seed propagated( ie , vegetatively propagated crops where the economic part is not seeds) eg : forage crops, tubers, sugarcane, ornamentals Crops with low 2n no. Allogamy / cross pollination eg : Poaceae against Leguminosae

6. STEP 1 Artificial induction and/or collection of naturally occuring pps and their maintanence . STEP 2 Detection of different kinds of pps . STEP 3 Isolation and handling of pps . STEPS IN PP BREEDING

7. PP breeding includes: 1. Monoploid /Haploid breeding 2. Autoploid breeding 3. Allopolyploid/ Amphi ( di ) ploid breeding 4. Aneuploid breeding

8. STEP 1 PRODUCTION OF HAPLOIDS By induced parthenogenesis Using incompatible or irradiated pollen, haploids can be obtained by parthenogenesis. Through wide crosses ( cross with distant species) eg : Hordeum vulgare х Elymus areanus Monoploid barley 1. MONOPLOID / HAPLOID BREEDING

9. Through chromosome elimination technique in distant crosses eg : Bulbosum technique H.vulgare х H.bulbosum (2n=2x=14) (2n=2x=14) Hybrid embryo Haploid barley (2n=x=7) ( H.bulbosum chr . eliminated) eg : Solanum nigrum x S.luteum

10. Cell culture/Tissue culture technique Anther culture technique by Guha and Maheswari Used in Datura , Nicotiana , Brassica , rice, wheat, triticale etc. Tanfeng is a haploidy derived rice variety developed in China(1976) Through pollen culture Haploid pollen grains develop into haploid plants. Nicotiana – readily responding in anther & pollen culture. Technique to be followed varies depending on the species.

11. STEP 2 DETECTION OF HAPLOIDS Detection through genetic markers Use of recessive & dominant genetic markers associated with seedling characters such as hypocotyl colour is useful in early detection of haploids. Eg : In potato, a dominant purple spot is present on haploid embryo-helps to distinguish at seed stage. Through plant morphology Haploid plants are inferior to diploids – shorter, less longer leaves, reduced in breadth, stomata & guard cells – smaller in size.

12. STEP 3 DIPLOIDISATION Colchicine treatment – most effective & widely used method. Acts as inhibitor of spindle formation during mitosis & causes duplication of homologus chromosomes Colchicine is readily soluble in cold water, alcohol and chloroform but less soluble in hot water. Used as aqueous solution – relatively unstable. So the solution prepared fresh before each application. Affects only dividing cells-applied to actively dividing meristematic cells repeatedly at brief intervals.

13. Methods of application: Seed treatment : Freshly prepared 0.2% solution applied for 1-10 days. Seedling treatment : At very young stage, seedlings are inverted and only the young shoots are dipped in colchicine solution & roots are protected;3-24hrs Application to growing apices : 0.1-1% solution applied to shoot apex using a dropper/cotton balls dipped in colchicine solution placed on shoot apices-repeated daily 0.5-1% colchicine + lemolin paste smeared on shoot apex-repeated 2-3 times per week. For woody plants, 1% colchicine with a wetting agent applied on shoot apices.

14. Includes triploid and tetraploid breeding TRIPLOID BREEDING Produced by crossing tetraploid and diploid (4n x 2n) Tetraploid as female – total qnty of seed low- proportion of 3n seeds high-produce vigorous hybrids Diploid as female-total qnty high-proportion of 3n seeds low 2. AUTOPOLYPLOID BREEDING

15. Triploids-pollen sterile-seedless-advantageous in watermelon In common planting, diploid planted to provide pollen for satisfactory seed set in triploid in 5:1 ratio

16. BANANA

17. Varieties Shonima & Swarna (2015) released from Kerala Agricultural University TRIPLOID WATERMELON

18. Variety Ocean TRIPLOID SUGARBEET 2x 3x

19. TV29 produces larger shoots & biomass; yields more cured leaf per unit area and tolerant to drought than available diploid varieties TRIPLOID CLONE OF TEA ( Camellia assamica )

20. TETRAPLOID BREEDING Produced by chromosome doubling from diploid plants

21. Possible in tobacco, Petunia etc. Autotetraploid maize has 43% more carotenoid content & vitamin A. Successful in forage crops, ornamentals etc. Pusa giant berseem -1 st autotetraploid variety (Egyptian clover) released for large scale cultivation – higher green fodder yield Vetiver variety – Sugandha – 11% more oil yield

22. AMPHIDIPLOID – Allopolyploids diploid for all genomes present. STEP 1 Production of F1 hybrids by interspecific and intergeneric crosses STEP 2 Chromosome doubling by colchicine 3. ALLOPOLYPLOID BREEDING

23. EVOLUTION OF BREAD WHEAT DD )

24. EVOLUTION OF TOBACCO

25. EVOLUTION OF COTTON

26. U’S TRIANGLE 4

27. RAPHANOBRASSICA Developed by Karpechenko Chr.doubling

28. TRITICALE Combines yield potential and grain quality of wheat & disease and environmental tolerance (including soil conditions) of rye

29. World’s 1 st interspecific cotton hybrid (1972) Developed by Dr. B. H. Katarki from Cotton Research Station, Dharwad , UAS, Bangalore G. hirsutum х G. barbadense ( Laxmi ) (SB 289 E) Varalaxmi VARALAXMI

30. 2n=38 Hybrid between Brassica campestris (syn. B.rapa ) and Raphanus sativus (fodder raddish ) RAPARADISH / BRASSICORAPHANUS

31. Irregular variation in chromosome no. By meiotic irregularities such as non-disjunction or lagging behind in metaphase plate result in n+1 & n-1 gametes. These gametes fertilized by normal gametes produce aneuploids . In desynaptic and asynaptic plants-a no.of univalents are seen in mid metaphase instead of bivalents which produce aneuploids Triploid plants produce aneuploid plants Tetrasomic plants produce aneuploid gametes resulting in aneuploid progeny. 4. ANEUPLOID BREEDING

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